Mechanical self-adjusting valve tappet



pril 15, 1958 G, Tl RANDOL 2,830,567

. MECHANICAL SELF-ADJUSTING VALVE TAPPET Filed Feb. 11, 1957 .nl lll United States atent l() assess? MECHANICAL SELF-ADJUSTHNG VLVE TAPPET Glenn T. Randol, Mountain Lake Parli, Md.

Application February 11, 1957, Serial No. 639,437

12 claims. (ci. '12s-s0) Y The present invention relates to valve tappets or litters adapted to maintain automatically substantially zero clearance in the valve drive train of an internal-com bustion engine. The invention particularly relates to mechanical self-adjusting valve tappets of improved operation and construction.

Mechanical valve litters presently used commercially do not provide automatic adjustment of the valve drive train or gear, nor automatic elimination of 'backlash in the valve operating mechanism of an internal-combustion engine. In mechanical tappet equipped drive trains, initial clearance commonly termed operating clearance, is provided between the engine camshaft and the stem of the valve. As the engine is operated, the aforesaid clearance is increased due to impact and wear of the engaging parts. Such increased clearance results in inei cient land noisy operation of the engine and requires a partial disassembly of the engine to adjust the tappets; that is, to temporarily correct the clearance to that required for the operating characteristics of the particular engine, by effecting manual adjustment in the drive train.

To avoid the necessity of frequent 'tappet `adjustment and to eliminate noisy an-d ineflicient operation of the engine, some commercial engines are equipped with hydraulic valve lifters which attempt to effect automatic adjustment of the valve drive gear to maintain zero clearance substantially in the train, so that in effect, the train functions as a solid body in opening the valves of the engine.

The general object of the present invention is to provide an improved valve lifter mechanism or tappet capable 4of constantly fand consistently maintaining a requisite operating tolerance thereby eliminating excessive backlash in the valve drive train of an internal-combustion engine, said operating tolerance being capable of modulation yto compensate for thermal changes in the en gine.

The primary object of the invention is to provide for incorporation in the valve drive train of a conventional internal-combustion engine, an improved automatically adjustable tappet of the mechanically-operated type.

Another object of the invention is to provide an improved mechanical valve tappet particularly adapted for use with a conventional valve operating engine-driven.l

cam, which tappe-t provides for maintaining silence of operation and afford long life for the cam itself and the mechanism operated thereby.

- Still another object of the invention is to provide an improved mechanical valve tappet `assembly that may be readily substituted for any and all valve lifter mechanisms presently used commercially, whether mechanical or hydraulic.

It is a further object of the invention to facilitate the attainment of the recited pri-mary objective by the provision of novel mechanical tappet mechanism of the compensating type which automatically adjusts to shorten or lengthen Kthe valve drive train to establish substantially ice zero clearance therein, so that when actuated by the cam on the engine camshaft, it functions to intermittently effect the cyclical opening and closing of a conventional engine poppet valve silently and efficiently at all operating speeds and thermal conditions of the engine.

A still further object of the invention is to provide an improved mechanical valve tappet Ithat is economical to manufacture, compact, readily assembled and disassembled, substantially uniformly actuated into and out `of engagement irrespective of the relative disposition of the members thereof, and effective to compensate for any undesirable relative movement between the members of the valve drive gear.

An important object of the present invention is to incorporate novel clutch mechanism between the two principal body members comprising the tappet, said mechanism having a plurality of movable elements of spherical configuration, for example, confined between oppositely disposed substantially parallel angular ramp elements carried respectively 'by the two body members whereby in the normal relaxed status of the tappet with the engine valve closed, the ramp elements carried by one of the members is withdrawn therefrom to accommodate 'the required adjustment of the tappet assembly, but upon movement of the tappet assembly to open an engine valve, relative movement of limited extent between the body members tends to roll the spherical elements on the ramps :and 'thus separate the ramp elements causing the two body members t-o be locked for conjoint movement during the lift portion of the `tappet cycle.

More specifically, the aforesaid novel clutch mechanism 4comprises a plurality, preferably three in number,

of frictional clutching elements encircling the lower endv portion of a cylindrical stem secured to and depending from the inner body member, each of said elements being of circular ring sector configuration and provided with a normal portion merging with a reduced portion offset from the exterior thereof. A hardened metallic shoe or race is fitted into a substantially rectangular recess provided in the exterior surface of the normal portion of each clutch element, each shoe being provided with a .depression having an angular working ramp surf-ace merging with a vertical surface, with the latter surface merging with a shortened angular surface to form a cavity, or channel for reception of said spherical element, such Ias a steel ball. The bore of the outer body' member is formed with a complemental annular channel having one side at an angle to provide a Working ramp normally substantially parallel to the working ramp carried by the shoe whereby said spherical elements are confined beeen said working ramps and effective upon actuating the outer `body member relatively to the inner body a predetermined extent to roll on said ramps to spread the same apart and thus carry the clutching elements radially inwardly into clamping relationship about the stem carried by the inner body member lto lock said members together for conjoint movement to open a selected engine valve. A helical compression spring is operably disposed between the inner body member bore and a washer engaging the upper ends of the aforesaid clutching elements for biasing said clutching elements downwardly to maintain operative engagement between the balls and ramps at all axially adjusted positions thereof relatively to the cylindrical stem, and also resisting upward movement of said clutching elements when the spherical elements are acting thereon to move them into clamping relationship with the inner body mem-ber stem. Thus when the engine valve is closed and the outer lbody member is engaging the base circle of the engine cam, this spring aids in forcing the spherical elements to released inactive status to enable tappet adjustments. Further, a lower normally preloaded spring operably disposed between the stem of the inner body member and the end wall of the bore in the outer body member, tends at all times to separate the body members and accommodate movement of said members toward each Iother which action of the latter spring also influences the sphericalelements to unlock the body members for subsequent compensating adjustments. Thus, it is seen that both springs aforesaid tend to elongate the tappet assembly, while the former has the additional function of stabilizing the clutch elements :about the stem and returning said clutching elements to normal released position.

It will be noted that a stabilizing clamping ring fitted in close tolerance relation on the inner body stem is provided to insure that relative axial and radial movements of the clutching elements will be uniformly simultaneous. Each `of the clutch elements is provided with an arcuate groove in the inner surface at the juncture of the reduced portion with the normal portion thereof. Fitted in this groove is the above ring, said groove being of such depth as not to interfere with free radial movement of the clutch elements into and out of clamping engagement with the stem aforesaid.

In the more comprehensive description of the invention to follow, additional features and advantages not specically set forth above will be apparent or noted, and the manner in which the invention achieves its objectives, reference being had to the accompanying drawing in which:

Figure l is a fragmentary transverse vertical section of a conventional V-type internal-combustion engine showing the overhead valve operating mechanism incorporating self-adjusting mechanical valve tappets constructed in accordance with the present invention.

Figure 2 is a longitudinal central section on an enlarged scale through a tappet of Figure l in the reposed or engine valve closed position;

Figure 3 is a transverse sectional view on an enlarged scale taken on the line 3--3 of Figure 2 showing details of the novel friction clutch mechanism;

Figure 4 is a fragmentary longitudinal section showing details of the novel friction clutch mechanism corresponding to the Figure 2 disclosure;

Figure 5 is a view similar to Figure 2 but showing the tappet inaugurating an engine valve opening cycle; and

Figure 6 isy an exterior elevation view of one of the clutching elements operably associated with the inner body member and showing the cooperating spherical element in dotted outline.

Referring now to the drawings, and particularly to Figure l, the invention is shown incorporated in a conventional V-type internal-combustion engine generally designated 13" having a plurality of poppet valves one of which is shown at 10 engaging its seat 11. A valve drive train or gear, indicated generally at VT, is provided for each valve of the engine, and is conventional in all respects except for the valve tappet mechanism T of the present invention, ywhich is embodied therein. The valve drive train VT extends between the valve 10 and a cam 12 on the camshaft 14 of the engine. The valve 10 may be of any known construction and that selected for illustration includes a stem portion 16, guided in a collar part 17, and having normally preloaded spring means 1S associated therewith normally tending to close the valve to its seated position. A rocker arm 19 pivotally mounted intermediate its ends on a suitable rock shaft 20 is adapted to bear at one end 21 thereof against the free end of the stem 16 when rotated in a counterclockwise direction, as viewed in the figure, to open valve 10 against the force of the spring means 18. The other end 22 of the'rocker arm 19 has a hemispherical recess, not shown, in its under surface to accommodate the outer rounded end of a push rod 24, the other end of which bears against a dished embossment 25 in the upper hollow end of the valve tappet T which will now be described as follows:

The valve tappet T, which is generally cylindrical in contour, is illustrated as slidably mounted in a bore 26 radially disposed, in respect to the axis of the camshaft 14, in the block of the engine E so that the inner end of the tappet bears on the surface of the cam 12 allotted thereto.

Referring now to Figures 2, 3, and 4 for a more complete understanding of the construction and functioning of the valve tappet T, it will be seen that each comprises as a first principal element, an outer body cup-shaped member or piston 28, preferably of composite construction, formed by a lower cup-shaped section 29 and an upper sleeve section 30, the lower section having a longitudinal bore 31, closed at its outer end to form an end wall 32, and its inner end terminating in a conical surface 33 hereinafter referred to as a working ramp or shoulder and a reduced diameter portion 34 externally threaded. The sleeve section 30 carries an internal annular groove 36 adjacent its outer end which is engaged by a split retainer ring 37, and the inner end is formed with a first counterbore 38 internally threaded for reception of the externally threaded portion 34 on the lower section 29 to provide a unitary assembly of the two sections to form the outer body member 28 best `demonstrated in Figures 2 and 5, and a second counterbore 39 connects the first counterbore and a longitudinal bore through the sleeve portion, the merging point of t le counterbore 39 and longitudinal bore 40 forming an angular shoulder 41 of conical configuration spaced from working ramp aforesaid to provide an internal channel or race 42 at the juncture of the two sections in assembled relationship.

The second principal element of the tappet T comprises the plunger 45 of cup-like form, the outer cylindrical surface thereof sliding in intimate contact with the surface of the bore 40 in the sleeve part 30. The plunger, therefore, is telescopically-related with respect to the outer body piston 28 due to its interftting relationship therewith, and has a longitudinal bore 46 open at its inner end and closed at its outer end to form an end wall 47, a centrally disposed threaded socket 43 is provided in the inner side of the end wall for reception of a reduced threaded shank 49 forming the outer terminus of a depending cylindrical stem 5t) coaxially disposed with respect to the bore 46, the embossment 25 above-mentioned being integral with the outer side of the end wall 47.

While I have shown a preferred construction of the piston member 28 as comprising the two sections 29, 30 threadedly connected to form a unitary element, it is desired to point out that this part may be optionally formed as an integral element. However, the former construction is believed to simplify the manufacturing operations required to produce this part, and therefore, lower the cost of the finished product.

The plunger 4S is constantly lbiased outwardly by a helical normally preloaded spring 52 tending to separate it from the piston Z3, the upper end of this spring bears on a seat 53 of inverted cup-shape configuration forming the inner terminus of the stern 50, and the lower end of which tits into a circular recess S4 formed in the inner face of the piston end wall 32 and thus reacts on the piston. The retainer ring 37 carried at the upper end of the outer body member 28 overlies a circular marginal portion on the outer side of the plunger end wall 47 for engagement thereby prior to installation of the tappet in the engine to prevent complete separation of the two principal elements of the tappet; namely, the interftting body members 23, 45, but when the tappet is installed in operative position the end wall 47 is always spaced inwardly from the retainer ring aforesaid as best shown in Figures 2 and 5 to enable relative axial adjustmentsv between the tappet body members to compensate for Wear and thermal changes resulting from engine operation as is Welll understood.

Movably disposed in encircling relationship with respect to the plunger stem 50 are novel friction clutch means generally designated FC comprising a plurality of circular ring sector clutch elements 56, three being illustrated exemplarily, as best seen in Figures 3 and 6. Each of these clutch elements has a lower enlarged segment 57 having a medially disposed rectangular recess 5? in the exterior curved surface thereof with the lower end of the recess open. Fitted into each of these recesses is a hardened metallic shoe 60 of corresponding oontour and provided with a transverse channel til formed with a wall 62 connecting an angular shoulder 63 and a working ramp or race 64 parallelly spaced with respect to the piston working ramp 33. Medially disposed in the inner curved surface ofeach of the sh-oes 60, is a transversely cut arcuate channel 65 for receiving a split clamping ring 66 frictionally encircling the plunger stern 59 to releasably stabilize the clutch elements 56 in all of their axially adjusted positions with respect to the plunger stem 5d for uniform simultaneous radial and axial movements to clutch and accommodate relative axial adjustments, respectively, between the two principal body parts. An abutment washer 68 encircling the stem atop the clutch elements 56 engages the latter to maintain them in circular alignment when moved into and out of engagement with the plunger stem Stl, under influence of a normally preloaded helical spring 69 surrounding the stem with its lower end bearing on the upper side of the washer aforesaid and the upper end acting on the inner face of the plunger end wall 47.

A like number of actuating` elements 70, preferably of spherical contour, are operatively disposed in the space Ybetween the working rams 33, 64 and maintained in correct operative relationship with respect to said working ramps by the action of the spring 69. Accordingly, spring 69 performs the important function of maintaining the clutch elements 56 at all times in operative engagement with the actuating elements 7), the latter functioning to convert axial thrust Iof the piston member 23 into radial inward movement of the clutch elements 56 to elect clamping engagement thereof about the plunger stem 50 to lock the piston 28 and plunger 45 together for conjoint movement responsive to the initial lift portion of the tappet cycle in operating a selected engine valve.

It is important to note here that the actuating elements 70 are normally disposed in the channels 42, 61 when the tappet T is in its relaxed position portrayed in Figures l and 2 with the engine valve 10 fully seated (closed), but initial lift movement of the piston member 23 tends to roll the balls 70 counterclockwise as indicated by the arrow in Figure 5 in a radially outward direction with respect to ramp 64 and radially inwardly on the ramp 33 causing the ramps to radially separate and impinge the connected clutch elements 56 on the plunger stem 5t! to thus frictionally lock the plunger stern and piston member together for simultaneous movement to open the selected engine valve as is understood.

The cam l2, in conventional fashion, includes a base circle portion '72 and opening and closing ramp portions 73, '7d respectively, and the apex of said ramp portions being designated 75, the latter establishing maximum lift (opening) of the engine valve 10.

The parts of the tappet assembly T are efliciently lubricated from the pressure lubricating system of the engine from return iiow via passageway 76 in the block of the engine, thence to annular channel 77 in the outer surface of the sleeve member 28, port 78 through the wall of said channel communicating with the bore 4t), to annular channel 79 in the cuter surface of the plunger 45 via port gil to bore 46, cross passageway 81 interconnecting axial passageway 32 in the plunger stem 5), bore 3l, port 33 through the wall of the lower section 29 and thence to the engine oil sump for recirculation by the engine-driven lubricating pump as is understood.

Operation The operation of the valve tappet mechanism of the present invention is as follows: v

With the engine valve 10 in closed position the various elements of the mechanism assume the relative positions illustrated in Figures l and 2. Here the helical spring 52 between the tappet body 28 and plunger 45 expands the tappet length between the push rod 24 and the base circle 72 of the cam 12 on camshaft 14 so that the lower wall end 32 of the outer member bears thereon with substantially the force exerted by the aforesaid spring. Also note that the upper spring 69 biases the clutching elements 56 into slipping contact about the stem 5o of the plunger member 45 and disposes the balls itl 4in the annular channels 42, 61 as shown with their working ramps 33, 64 respectively contacting diametrical points on the balls 79 whereby the stem 50 carried by the plunger body part 45 is movable relatively to the outer body part 28 to effect the necessary adjustment of the relative disposition of the two principal body parts to eliminate backlash in the valve drive gear VT external to the predetermined operating clearance necessary to operate the outer body part relatively to the inner body plunger to roll the balls on their opposed ramps thus forcing the clutching elements 56 radially inwardly into frictionally locking engagement about the plunger stern 50 for unison movement of the body parts to open a selected engine valve responsive to the lift portion of the tappet cyclical movement.

The entire assembly is under all operating conditions properly lubricated from the pressure lubricating system of the engine by the overllow oil routed via the passageway 76 in the engine block and communicating with the various ports and passages aforesaid of the tappet assembly and thence to the engine sump for recirculation as is understood.

As the engine cam 12 rotates in the direction indicated by the arrow as viewed in the figures, the opening ramp 73 of the cam merges with the base circle and operatively engages the under side of the end 32 of the tappet body 28 and begins to lift the same either with a quick lift, if the cam is designed for the conventional type of valve tappet, or with a slower more gentle lift if the cam is especially designed for tappets of the type of the present invention. Under these circumstances the movement of the tappet T being resisted by the engine valve closure spring 18 through the push rod 24, tends to roll the balls counterclockwise on their ramps with consequent forcing of the clutching elements 56 radially inwardly into frictional locking engagement with the plunger stem 50 whereby the tappet assembly T moves as a solid unit to open the engine valve. This condition obtains through maximum lift of the engine cam and subsequent closed condition of the engine valve wherein the outer body member engages the base circle 72 of the cam 12 enabling the two body parts to relax under influence of the lower compression spring 52 causing the balls 70 to reverse their movement on the associated working ramps so that the clutching elements 56 can relax clutching engagement with the plunger stern, and thus accommodate restoration of the operating clearance as determined byl the thermal condition of the engine, and/or any adjustment in the length of the tappet body to eliminate any excessive backlash in readiness for another valve opening cycle as described.

As the cam 12 progresses from maximum lift point above to the released or valve closing ramp 74, the tappet is lowered and with it the engine valve 10 is closed by action of the spring 18. Under these circumstances the downward movement of the tappet T is effected with the two principal body parts 28, 45 moving in unison due to the locking effect of the ball-actuated clutching elements 56 about the stem St) of the inner plunger member-'45. Upon cessation of tappet movement as the tap-y pet enters the base circle 7 2 of the engine cam, the lower spring 52 within the tappet body effects relative movement of the body parts to unclutch the clutching elements 56 responsive to the balls rolling reversely on their pairs of ramps 33, 64 and simultaneously with this action, the upper spring 69 is effective to cause the clutching elements 56 to follow the reverse action of the balls and thus re-establish the clutching elements 56 in relaxed status with respect to the stem 50 and the ball races car ried by said elements, in the position shown in Figure 2 wherein the two body parts are capable of adjusting in either direction relatively to each other to compensate for under or over-adjustment as may be the case.

The upper spring 69 is not suficiently strong to interfere with the radial movement of the clutching elements 56 toward and away from the stem Si), but should be preloaded sufficiently to stabilize the three clutching elements from axial movement when the locking action of the balls is inaugurated. The operating clearance is defined by the limited axial movement of the outer body member 28 relatively to the inner plunger stem 50 to bring about effective frictional locking engagement of the two body parts as described. This movement axially of the outer body member to actuate the clutching elements in the manner described, causes a possible slight axial movement of the clutching elements prior to locking said elements radially inwardly about the stem, due to the resilient nature of the upper spring 69. Such axial movement of the clutching elements can be minimized by installing the upper spring under proper preloaded status. The caged condition of the balls as best illustrated in Figure 4 prevents the action of the upper spring from displacing the clutching elements S6 since these elements are always in engagement with the surface of the cylindrical stem Si). Thus the clutching elements 56 are conned in operative position between the stem 50 and the balls 70. The slight spacing of the clutching elements as shown in Figure 2 is done to clearly portray disengaged condition thereof from the stem 50 but under actual operating conditions, the clutching elements touch the plunger stern at all times.

Operational summary Although the manner in which my invention achieves its objectives should be manifest from the foregoing description augmented by an inspection of the drawing, a brief restatement is deemed apropos, and will be given as follows:

What will be considered an engine valve opening cycle,

will now be described with reference to the tappet of the instant invention. Assuming the engine is running and the selected valve closed as portrayed in Figure 2, such a cycle comprises rotation of the cam 12 from the Figure 2 position in the direction indicated by the arrow to the position of Figure wherein the opening ramp 73 of the cam has initially engaged the under side of the end wall 32 of the piston body member 28 to operate the clutch means FC into frictional locking engagement about the` plunger stem 50. This engaging operation of the clutch means is brought about by the relative axial thrust (operating clearance) of the piston member 28 on the actuating balls 70 which in turn effects a radial inward movement of the clutch elements 56 due to the rollingthrust action of the balls on their opposed working ramps 33, 64. This action of the balls tends to separate the ramps aforesaid from their normal disposition portrayed in Figure 2 and is induced by the opposition of the spring 69 to axial movement of the clutch elements in maintaining the working ramps in intimate Contact with diametrical points on the balls. Continued rotation of the engine cam brings the apex 75 of the cam to the center of the bottom wall 32 at which point maximum lift of the tappet assembly T has been reached and as the apex passes the center point aforesaid, the closing ramp 74 engages the under side of the end wall 32 to lower the tappet assembly under inuence of the valve spring means 18 into engagement with the base circle 72 to fully seat (close) the valve 1t) as portrayed in Figures 1 and 2.

Upon full closure of the engine valve, spring 52 tends to relax the parts of the tappet which introduces sufficient accumulated tolerances between the parts to reinstate the operating clearance in readiness for an ensuing valve opening cycle in the manner above-described.

It is important to note that with the operating clearance re-established the alignment ring 66 accommodates relative adjustments between the principal body parts 28, 45 to shorten or lengthen the tappet as is understood, and at the same time frictionally holds the working ramps 33, 64 in engagement with the actuating balls 70 in cooperation with the force exerted by the spring 69, so that an ensuring valve opening cycle, when inaugurated, incrementally moves tlie clutch elements 56 inwardly radially into clamping relation around the plunger stem 50 with the spring 69 axially stabilizing the said elements to prevent introduction of excessive operating clearance in the mechanism T.

It will be noted that two elements operate to eliminate any backlash in the valve drive train VT, and both function during the time the tappet T is riding the base circle '72 of the cam 12. The iirst of these is the compression spring 52 and the second is the compression spring 69, both tending to separate the principal body part or actually elongate the tappet assembly. Spring 52 acts directly between the plunger assembly 45 and piston Z8, while the spring 69 is effective via the working ramps 33, 64 and interconnecting balls 79. The biasing effect, however, of the latter spring is much lighter than the other spring, and therefore, while serving to co-opcrate with spring 52 its function to assist in separating the principal body parts is not essential to the operativeness of the present novel tappet as its primary function is to maintain the clutch elements 56 and the working ramps 33, 64 in contact with the interconnecting balls 70 at all axially adjusted positions of the clutch elements with respect to the plunger stem 50.

In installing the valve tappet mechanism of the present invention, it makes no difference whether the engine be hot or cold during installation since over-adjustment which would normally occur if the engine were hot during installation, and under-adjustment, which would'normally occur if the engine were cold during installation, are readily compensated for and eliminated by the automatic operation of the present tappet mechanism T.

The present invention is particularly adapted to be utilized in the replacement of all valve tappet mechanisms whether mechanical or hydraulic. While it is preferred that the cam design be conventional, as shown in the drawing, it is clear that the present invention will operate satisfactorily with the particular cam design presently used for commercial hydraulic valve lifters where the opening ramp gives a rapid rise to the tappet in order to provide the hydraulic impact to insure closure of the tappet check-valve substantially at the instant of initial tappet lift.

Considering the terminology used in the foregoing description and in the appended claims, the identifying expressions and/or terms employed are intended to convey meanings which include the range of reasonable equivalents in the patent sense. For example, the expressions wear, backlash, and lost-motion are intended to convey similar meanings with respect to excessive idle travel within the valve drive gear, while such expressions as operating clearance, limited relative movement, initial movement, axial movement, etc., relate to the limited relative operaitng movement within the tappet mechanism as is understood. The terms upperf upward, lower, bottom, verticaL outer, inner, top, and other directional words or characters are intended to have only relative connotation for convenience in describing ,the structure as illustrated in the drawings,

and are not intended to be interpreted as establishing a definite position of the tappet mechanism or as' requiring any special orientation with regard to associated structure external to the present disclosure.

In view of the foregoing description augmented by the drawing, it should be evident that my invention discloses a new and novel tappet construction which is eflcient, simple in design, and which is adapted to achieve its objectives set forth above.

Whereas the drawing illustrates, and the above description sets forth the preferred embodiment of my invention, it is to be understood that the invention contemplates any variations of structure, and equivalents or modications which may fall within the scope of the appended claims. v

Having thus described my invention, I claim:

1. A mechanical valve tappet assembly operably disposed in an internal-combustion engine between a cam on the camshaft and the stern of a spring-loaded poppet-type valve, said assembly including in combination: a cam-actuated tappet body having a longitudinal cylindrical counterbore merging with a coaxial bore closed at one end; a hollow plunger closed at one end and open at the other and slidably disposed in the tappet body counterbore with the exterior of its closed end efective to act on the valve stem; a cylindrical element rigid at one end with the closed end of the plunger and projecting through the open end thereof; a spring seat formed on the other end of the cylindrical element; normally preloaded compression spring means operably effective on the spring seat andinner face of the closed end of the tappet body for separating the plunger and body and accommodate their relative movement toward each other; an annular internal angular shoulder formed at the mergence of the counterbore and coaxial bore; a plurality of clutch elements encircling the cylindrical element; complemental annular external shoulders carried by each clutch element in substantially parallel spaced relationship with respect to the body annular shoulder; an internal arcuate channel carried by each of the clutch elements; a resilient split ring fric-- tionally disposed on the cylindrical element for engaging the arcuate channels aforesaid to stabilize said elements in circular alignment at all adjusted axial positions thereof relatively to the cylindrical element and accommodate radial movement of the same relatively to the cylindrical element; clutch actuating elements operably disposed between the internal and external shoulders aforesaid; normally preloaded compression spring means encircling the cylindrical element and effective on the inner face of the closed end of the plunger and the confronting ends of the said clutch elements to maintain the annular shoulders and clutch actuating elements in intimate contact at all adjusted axial positions thereof, said clutch actuating elements being effective to transmit thrust from the internal piston shoulder to the external shoulders to move the clutch elements radially inwardly into frictional clamping relationship about the cylindrical element for interlocking the tappet body and plunger responsive to limited camactuation of the tappet body relatively to the plunger prior to opening a selected engine valve.

2. A mechanical compensating tappet comprising a pair of interlitting relatively movable cylindrical members, one member being provided with a longitudinal cylindrical bore open at one en d and closed at the other, and the other member having a cylindrical longitudinal counterbore merging with a coaxial bore closed at one end; a cylindrical element secured to and depending from the closed end of said one member; normally preloaded spring means for axially elongating said members relatively to each other; a plurality of movable clutch elements in surrounding relation with respect to said cylindrical element; an angular circular internal ramp formed at the mergence of the said counterbore and coaxial bore; a complemental ramp formed on the exterior of each clutch element in confronting spaced relation with respect to the circular ramp; and movable clutch actuating elements operably disposed between the complemental and circular ramps for moving the clutch elements inwardly radially into wedging engagement with the cylindrical element to temporarily interlock the said members responsive to the initial lift portion of the tappet cycle.

3. In a mechanical compensating tappet comprising, in combination; a pair of relatively movable interfitting body members, biasing means operably disposed between said members to effect relative separation thereof and to accommodate relative adjustment toward each other, friction clutch means including a driving and a radially movable driven element carried respectively by said members, complemental friction surfaces on one of said members and the driven element for frictionally locking said members together for conjoint movement, and means acting simultaneously on said elements to radially separate the same to effect engagement of the frictional surfaces on the driven element and said one member in response to initial relative movement of the other of said members.

4. In a mechanical compensating tappet for use in a valve drive train for opening and closing a spring-loaded valve of an engine, comprising: a pair of telescopicallyrelated body members movable relatively to eachother and adapted for incorporation in said valve drive train, normally preloaded spring means operably disposed between said members for accommodating relative adjustments therebetween to establish zero clearance substantially in the valve drive train in the closed position of the engine valve, engine-driven cam means for operably engaging one of said members for opening said engine valve, friction clutch means having driving and driven elements carried respectively by said members, and means operably interconnecting said elements to separate the same to frictionally clutch said members together for conjoint movement responsive to initial relative movement of said one member by said cam means.

5. In a mechanical compensating tappet for valves of internal-combustion engines including a cam-actuated tappet body having a longitudinal cylindrical counterbore merging with a coaxial bore, closed at one end and openat the other; a plunger reciprocably mounted in said counterbore and provided with a clutching surface adjacent its inner end; means effective between the tappet body and plunger for limiting relative axial displacement therebetween; normally preloaded spring means for axially elongating the tappet body and plunger relatively to each other; a movable clutchelement having a com- `plemental clutching surface in confronting relation to the clutching surface on the plunger for engagement therewith; means for stabilizing the clutch element when dis engaged in a predetermined spaced relation with respect to the clutching surface on the plunger; means operably incorporated between the tappet body and clutch element for imparting radial movement to the clutch element to clutch the plunger and tappet body together for conjoint movement responsive to limited relative axial movement of the tappet body during the initial lift portion of the tappet cycle to open the selected engine valve. Y

6. In a mechanical compensating tappet of the character described, a cup-shaped piston reciprocable responsive to the rotation of a cam on the camshaft of an internal-combustion engine to open and close a springloaded engine valve, a spring supported plunger slidably mounted in the piston for limited axial movement with respect thereto; a conical working segment on the piston;

ments operatively engaging the angular and conical seg ments aforesaid to effect their separation causing the clutch elements to frictionally engage the clutching surfaceA on the plunger and lock the plunger and piston together for conjoint movement responsive to predetermined relative axial movement of the piston with respect to the plunger induced by rotation of the camshaft at the inauguration of an engine valve opening cycle.

7. A mechanical compensating tappet according to claim 6 including a split friction ring encircling the plunger stem, and an internal arcuate channel in each of the clutch elements for reception of said ring to stabilize the clutch elements when disengaged in their different axially adjusted positions with respect to the plunger stem.

8. A mechanical compensating tappet according to claim 7 including a normally preloaded spring acting on the clutch elements for maintaining the latter in operative relationship with respect to the movable elements aforesaid.

9. A mechanical compensating tappet according to claim 8 including an annular internal groove adjacent the outer end of the piston, and a split retainer ring engaging said groove and overlying the outer end of the plunger to limit axial separation of the plunger and piston.

10. A mechanical compensating tappet including in assembly: a cup-shaped composite piston comprising a lower and upper section reciprocable in a cylinder of an internal-combustion engine responsive to the rotation of the engine camshaft for opening and closing a springloaded engine valve, said lower section terminating at its inner end in a reduced externally threaded portion and having a central axial bore forming an end wall at its outer end with its inner end tapered to form an angular working ramp, the upper section being provided with a complemental internally threaded portion at its inner end for engaging the lower section threaded portion to form the two-sectioned piston aforesaid, an angular annular shoulder formed internally at the inner end of the upper section, spaced from the lower section ramp and interconnected by a bottom wall to form an annular internal channel therebetween, an internal annular groove adjacent the outer end of the upper section, and a larger longitudinal bore through the upper section merging coaxially with the axial bore in the lower section; a hollow plunger closed at its outer end to form an end wall and open at its inner end and including a threaded socket formed centrally in the end wall and a depending stem disposed in said hollow having a reduced threaded shank for engaging the socket threads to tix the stem to the plunger; a split retainer ring engaging the piston internal groove for limiting relative separation of the plunger and piston; a plurality of movable clutch elements encircling said stem, said elements being of circular ring sector cross section and each being provided with an internal arcuate channel, a lower enlarged segment formed with an exterior recess for reception of a detachable shoe formed exteriorly with a channel spaced from the channel of the piston and having an angular side wall connected by a bottom wall to a complemental working ramp parallelly spaced from the piston working ramp; a split clamping ring encircling the plunger stem for engaging the arcuate channels of the clutch elements to frictionally support said elements in circular alignment at all axially adjusted positions thereof with respect to the plunger; an abutment washer encircling the plunger stem in engagement with the upper ends of the clutch elements; a normally preloaded compression spring operably disposed in the hollow of the plunger around its stem and acting on the end wall of the plunger and washer for operatively stabilizing the clutch elements at all axially adjusted positions relatively to the stem; normally preloaded compression spring means operably disposed between the inner end of the plunger stem and end wall of the piston lower section for elongating the piston and plunger with respect to each other and accommodate relative movement toward each other; and a movable spherical element operably incorporated between the piston channel and each channel in the plunger shoes, in operative engagement with the working ramps aforesaid for converting initial axial thrust of the piston relatively to the plunger into radial inward movement of the clutch elements to effect simultaneous clamping engagement thereof about the plunger stem to frictionally lock the piston and plunger together for conjoint movement responsive to the initial lift portion of the tappet cycle induced by rotation of the engine camshaft to open a selected engine valve.

ll. A mechanical compensating tappet according to claim l0 including a lubricating system deriving lubricant from a line fed by the pressure lubricating system of the engine and comprising: an annular external channel on the upper section of the composite piston communicating with the feeding line aforesaid, a port through the wall of said channel communicating with an annular external channel on the plunger, a port through the wall of the plunger channel communicating with the hollow of said plunger, an axial passageway in the plunger stem open at its inner end and closed at its outer end, a cross passageway intersecting the stem axial passageway adjacent its closed end; and a port through the side wall of the lower section of the piston connecting the axial bore thereof to the engine sump.

12. A mechanical compensating tappet according to claim l0 including an upstanding circular embossment integral with the exterior of the plunger end wall and formed with a concavity for the reception of the lower rounded end of a valve push rod for actuating the engine valve in opposition to its spring load.

References Cited in the tile of this patent UNITED STATES PATENTS 2,765,783 Randol Oct. 9, 1956 

